From 19bc8e64a4dbdc613503e2446b9e124e92d525cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E7=88=B1=E7=89=B9=E6=AF=8F=E7=BE=8A=E9=98=9F?=
 <t2026104239910027@eduxiji.net>
Date: Sat, 27 Jun 2026 17:23:50 +0800
Subject: [PATCH] =?UTF-8?q?fix:=20defineProperty=20=E7=BA=AF=E5=B1=9E?=
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---
 crates/oxide_builtins/src/object.rs                   | 11 +++++++----
 .../tests/define_property_descriptor_tests.rs         |  8 ++++----
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/crates/oxide_builtins/src/object.rs b/crates/oxide_builtins/src/object.rs
index f576d03..3126be3 100644
--- a/crates/oxide_builtins/src/object.rs
+++ b/crates/oxide_builtins/src/object.rs
@@ -287,10 +287,13 @@ pub fn object_define_property<H: VmHost>(vm: &mut H, args: &[u8]) -> NativeResul
         }
     } else {
         if existing_pos.is_none() {
-            return NativeResult::Err(crate::error::create_type_error(
-                vm,
-                "Cannot define new property without value or accessor",
-            ));
+            if vm
+                .define_data_property(obj, si, JsValue::undefined(), PropAttributes::new(false, enumerable, configurable))
+                .is_err()
+            {
+                return NativeResult::Err(crate::error::create_type_error(vm, "Cannot define property"));
+            }
+            return NativeResult::Ok(obj_val);
         }
         let is_accessor = existing_meta.map(|m| m.is_accessor).unwrap_or(false);
         let writable = existing_meta.map(|m| m.attributes.writable()).unwrap_or(true);
diff --git a/crates/oxide_vm/tests/define_property_descriptor_tests.rs b/crates/oxide_vm/tests/define_property_descriptor_tests.rs
index 7548245..bd53e7b 100644
--- a/crates/oxide_vm/tests/define_property_descriptor_tests.rs
+++ b/crates/oxide_vm/tests/define_property_descriptor_tests.rs
@@ -92,11 +92,11 @@ fn get_own_property_descriptor_accessor_fields() {
     );
 }
 
-// -- New property without value or accessor throws --
+// -- New property without value or accessor defaults to data descriptor (ES spec behavior) --
 #[test]
-fn define_property_new_without_value_throws() {
-    let result = eval_str("var obj={}; Object.defineProperty(obj,'x',{enumerable:true})");
-    assert_err_contains(result, "Cannot define new property without value or accessor");
+fn define_property_new_attributes_only_defaults_value_undefined() {
+    let r = eval_str("var obj={}; Object.defineProperty(obj,'x',{enumerable:true}); obj.x").unwrap();
+    assert!(r.is_undefined(), "new prop with only enumerable should default value to undefined, got {:?}", r);
 }
 
 // -- Partial configurable on existing property preserves value --